import java.util.ArrayList;
import java.util.List;

public class Test2 {
    public static void main(String[] args) {
        /*
        Dog dog = new Dog();
        //向上转型
        Animal animal1 = dog;
        if(animal1 instanceof Dog){
            dog = (Dog)animal1;
            dog.lookDoor();
        }
         */
        List<String> list = new ArrayList<>();
    }
}
